Method and apparatus for trimming an internal combustion engine

ABSTRACT

A fuel injection control system and method for trimming an internal combustion engine during a fuel injection event based upon engine operating conditions, the control system including an electronic controller in electrical communication with the engine, the controller being operable to detect the operating mode of each injector of the engine and alter each injector operating mode as desired.

TECHNICAL FIELD

[0001] This invention relates generally to electronically controlledfuel injection systems and, more particularly, to a method and apparatusfor determining a desired duration at which to set a delay duringmultiple shot fuel injections for each injector device of the injectionsystem.

BACKGROUND ART

[0002] Electronically controlled fuel injectors are well known in theart including hydraulically actuated and mechanically actuatedelectronically controlled fuel injectors. An electronically controlledfuel injector typically injects fuel into a specific engine cylinder asa function of an injection signal received from an electroniccontroller. These signals include waveforms that are indicative of adesired injection rate as well as the desired timing and quantity offuel to be injected into the cylinders.

[0003] Emission regulations pertaining to engine exhaust emissions areincreasingly becoming more restrictive throughout the world including,for example, restrictions on the emission of hydrocarbons, carbonmonoxide, particulate and nitrogen oxides (NO_(x)). Tailoring the numberand the parameters of the injection fuel shots during a particularinjection event are ways in which to control emissions and meet suchemission standards. As a result, techniques for generating split ormultiple fuel injections during an injection event have been utilized tomodify the burn characteristics of the combustion process in an attemptto reduce emissions and noise levels. Generating multiple injectionsduring an injection event typically involves splitting the total fueldelivery to the cylinder during a particular injection event into two ormore separate fuel injections, generally referred to as a pilotinjection fuel shot, a main injection fuel shot and/or an anchorinjection fuel shot. As used throughout this disclosure, an injectionevent is defined as the injections that occur in a cylinder during onecycle of the engine. For example, one cycle of a four cycle engine for aparticular cylinder, includes an intake, compression, expansion, andexhaust stroke. Therefore, the injection event in a four stroke engineincludes the number of injections, or shots, that occur in a cylinderduring the four strokes of the piston. The term shot as used in the artmay also refer to the actual fuel injection or to the command currentsignal to a fuel injector or other fuel actuation device indicative ofan injection or delivery of fuel to the engine. At different engineoperating conditions, it may be necessary to use different injectionstrategies in order to achieve both desired engine operation andemissions control.

[0004] In the past, the controllability of split or multiple injectionshas been somewhat restricted by mechanical and other limitationsassociated with the particular types of fuel injectors utilized. Forexample, when delivering a split or multiple injection current waveformto a plurality of fuel injectors, some injectors will actually deliverthe split fuel delivery to the particular cylinder whereas someinjectors will deliver a boot fuel delivery. A boot type of fueldelivery generates a different quantity of fuel as compared to a splittype fuel delivery since in a boot type delivery, the fuel injectionflow rate never goes to zero between the respective fuel shots.Conversely, in a split fuel delivery, the fuel injection flow rate doesgo to zero between the respective fuel shots. As a result, more fuel isdelivered in a boot type delivery as compared to a split fuel delivery.Even with more advanced electronically controlled injectors, duringcertain engine operating conditions it is still sometimes difficult toaccurately control fuel delivery.

[0005] When dealing with split or multiple fuel injection and thegeneral effects of a boot type fuel delivery and the fuel injection rateshaping which results therefrom, desired engine performance is notalways achieved at all engine speeds and engine load conditions. Basedupon operating conditions, the injection timing, fuel flow rate andinjected fuel volume are desirably optimized in order to achieve minimumemissions and optimum fuel consumption. This is not always achieved in amultiple injection system due to a variety of reasons includinglimitations on the different types of achievable injection ratewaveforms and the timing of the fuel injections occurring during theinjection events. As a result, problems such as injecting fuel at a rateor time other than desired within a given injection event and/orallowing fuel to be injected beyond a desired stopping point canadversely affect emission outputs and fuel economy. From an emissionsstandpoint, either a split or boot fuel delivery may be preferable,depending on the engine operating conditions.

[0006] In a system in which multiple injections and different injectionwaveforms are achievable, it is desirable to control and deliver anynumber of separate fuel injections to a particular cylinder so as tominimize emissions and fuel consumption based upon the operatingconditions of the engine at that particular point in time. This mayinclude splitting the fuel injection into more than two separate fuelshots during a particular injection event and/or adjusting the timingbetween the various multiple fuel injection shots in order to achievethe desired injector performance, that is, a split or a boot type fueldelivery, based upon the current operating conditions of the engine.

[0007] Accordingly, the present invention is directed to overcoming oneor more of the problems as set forth above.

DISCLOSURE OF THE INVENTION

[0008] In one aspect of the present invention, there is disclosed anelectronically controlled fuel injection system which is capable ofdelivering multiple fuel injections to a particular cylinder of aninternal combustion engine during a single injection event. The presentsystem includes means for variably determining whether two, three, ormore separate fuel injections or fuel shots are desired during a fuelinjection event at given engine operating conditions including enginespeed and engine load. In this regard, in a preferred embodiment, fuelis apportioned between a first or pilot shot, a second or main shot anda third or anchor shot, each separate fuel injection shot beingdelivered when the cylinder piston is located within a predeterminedrange during a particular piston stroke. The present system alsoincludes means for varying the timing and fuel quantity associated withthe main shot, the timing and the fuel quantity associated with theanchor shot, as well as the duration of the anchor delay, based upon theoperating conditions of the engine.

[0009] Under certain operating conditions, the proximity of the main andanchor shots and the resultant internal injector hydraulics and/ormechanics leads to a rate shaping effect of the third or anchorinjection. As a result, although the first or pilot injection, whenused, is typically a distinct injection as compared to the second, ormain, and the third, or anchor, injections, a distinct anchor injectionis not always apparent. The present invention enables determination asto whether a given injector is delivering a distinct third shot and,based upon considerations such as engine performance, minimization ofemissions, injector durability and so forth, the present system altersthe anchor shot delay, if necessary, to achieve the desired injectorperformance.

[0010] These and other aspects and advantages of the present inventionwill become apparent upon reading the detailed description in connectionwith the drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a better understanding of the present invention, referencesmay be made to the accompanying drawings in which:

[0012]FIG. 1 is a schematic view of an electronically controlledinjector fuel system used in connection with one embodiment of thepresent invention;

[0013]FIG. 2 is an exemplary schematic illustration of a currentwaveform sequentially aligned with a corresponding fuel injection ratetrace;

[0014]FIG. 3 is a schematic profile illustrating how the volume of fuelinjected varies according to the duration of the anchor delay;

[0015]FIG. 4a is a first segment of a logic diagram showing theoperation of the present invention; and

[0016]FIG. 4b is a second segment of a logic diagram showing theoperation of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0017] Referring to FIG. 1, there is shown one embodiment of ahydraulically actuated electronically controlled fuel injection system10 in an exemplary configuration as adapted for a direct-injectioncompression ignition engine 12. Fuel system 10 includes one or moreelectronically controlled fuel injectors 14 which are adapted to bepositioned in a respective cylinder head bore of the engine 12. Whilethe embodiment of FIG. 1 applies to an in-line six cylinder engine, itis recognized and anticipated, and it is to be understood, that thepresent invention is also equally applicable to other types of enginessuch as V-type engines and rotary engines, and that the engine maycontain any plurality of cylinders or combustion chambers.

[0018] The fuel system 10 of FIG. 1 includes an apparatus or means 16for supplying actuation fluid to each injector 14, an apparatus or means18 for supplying fuel to each injector, electronic control means 20 forcontrolling the fuel injection system including the manner and frequencyin which fuel is injected by the injectors 14 including timing, numberof injections per injection event, fuel quantity per injection, timedelay between each injection, and the injection profile. The system mayalso include apparatus or means 22 for recirculating fluid and/orrecovering hydraulic energy from the actuation fluid leaving eachinjector 14.

[0019] The actuating fluid supply means 16 preferably includes anactuating fluid sump or reservoir 24, a relatively low pressureactuating fluid transfer pump 26, an actuating fluid cooler 28, one ormore actuating fluid filters 30, a high pressure pump 32 for generatingrelatively high pressure in the actuation fluid, and at least onerelatively high pressure actuation fluid manifold or rail 36. A commonrail passage 38 is arranged in fluid communication with the outlet fromthe relatively high-pressure actuation fluid pump 32. A rail branchpassage 40 connects the actuation fluid inlet of each injector 14 to thehigh-pressure common rail passage 38.

[0020] The apparatus 22 may include a waste accumulating fluid controlvalve 50 for each injector, a common recirculation line 52, and ahydraulic motor 54 connected between the actuating fluid pump 32 andrecirculation line 52. Actuation fluid leaving an actuation fluid drainof each injector 14 would enter the recirculation line 52 that carriessuch fluid to the hydraulic energy recirculating or recovering means 22.A portion of the recirculated actuation fluid is channeled tohigh-pressure actuation fluid pump 32 and another portion is returned toactuation fluid sump 24 via recirculation line 34.

[0021] In a preferred embodiment, the actuation fluid is enginelubricating oil and the actuating fluid sump 24 is an engine lubricationoil sump. This allows the fuel injection system to be connected as aparasitic subsystem to the engine's lubricating oil circulation system.Alternatively, the actuating fluid could be fuel.

[0022] The fuel supply means 18 preferably includes a fuel tank 42, afuel supply passage 44 arranged in fluid communication between the fueltank 42 and the fuel inlet of each injector 14, a relatively lowpressure fuel transfer pump 46, one or more fuel filters 48, a fuelsupply regulating valve 49, and a fuel circulation and return passage 47arranged in fluid communication between each injector 14 and fuel tank42.

[0023] Electronic control means 20 preferably includes an electroniccontrol module (ECM) 56, also referred to as a controller, the use ofwhich is well known in the art. ECM 56 typically includes processingmeans such as a microcontroller or microprocessor, a governor such as aproportional integral derivative (PID) controller for regulating enginespeed, and circuitry including input/output circuitry, power supplycircuitry, signal conditioning circuitry, solenoid driver circuitry,analog circuits and/or programmed logic arrays as well as associatedmemory. The memory is connected to the microcontroller or microprocessorand stores instruction sets, maps, lookup tables, variables, and more.ECM 56 may be used to control many aspects of fuel injection including(1) the fuel injection timing, (2) the total fuel injection quantityduring an injection event, (3) the fuel injection pressure, (4) thenumber of separate injections or fuel shots during each injection event,(5) the time intervals between the separate injections or fuel shots,(6) the time duration of each injection or fuel shot, (7) the fuelquantity associated with each injection or fuel shot, (8) the actuationfluid pressure, (9) current level of the injector waveform, and (10) anycombination of the above parameters. Each of such parameters may bevariably controllable independent of engine speed and load. ECM 56receives a plurality of sensor input signals S₁-S₈ which correspond toknown sensor inputs such as engine operating conditions including enginespeed, engine temperature, pressure of the actuation fluid, cylinderpiston position and so forth that may be used to determine the precisecombination of injection parameters for a subsequent injection event.

[0024] For example, an engine temperature sensor 58 is illustrated inFIG. 1 connected to engine 12. In one embodiment, the engine temperaturesensor includes an engine oil temperature sensor. However, an enginecoolant temperature sensor can also be used to detect the enginetemperature. The engine temperature sensor 58 produces a signaldesignated by S₁ in FIG. 1 and is input to ECM 56 over line S₁. In theparticular example illustrated in FIG. 1, ECM 56 issues control signalS₉ to control the actuation fluid pressure from pump 32 and a fuelinjection signal S₁₀ to energize a solenoid or other electricalactuating device within each fuel injector thereby controlling fuelcontrol valves within each injector 14 and causing fuel to be injectedinto each corresponding engine cylinder. Each of the injectionparameters are variably controllable, independent of engine speed andload. In the case of fuel injectors 14, control signal S₁₀ is a fuelinjection signal that is an ECM commanded current to the injectorsolenoid or other electrical actuator.

[0025] It is recognized that the type of fuel injection desired duringany particular fuel injection event will typically vary depending uponvarious engine operating conditions. In an effort to improve emissions,it has been found that delivering multiple fuel injections to aparticular cylinder during a fuel injection event at certain engineoperating conditions achieves both desired engine operation as well asemissions control.

[0026]FIG. 2 shows an exemplary current wave trace or waveform 60 havinga pilot current pulse 62, a main current pulse 64, and an anchor currentpulse 66 sequentially aligned with a rate trace profile 68 illustratingthe fuel injection flow rate. The rate trace profile 68 includes a pilotshot 70 responsive to the pilot pulse 62, a main shot 72 responsive tothe main pulse 64 and an anchor shot 74 responsive to the anchor pulse66.

[0027] An anchor delay current signal 76, separating the main and anchorpulse signals 64 and 66, produces a corresponding anchor delay 78 whenthe main and anchor shots 72 and 74 operate in a split condition, i.e.,the fuel flow rate is significantly reduced for the duration of theanchor delay current signal as illustrated by the split profile segment80 shown in FIG. 2. In one embodiment, for an injection signal utilizingtwo injections, the injections may be referred to generically as being afirst injection, e.g., main injection, a second injection, e.g., ananchor injection, and an injection delay, e.g., an anchor delay.

[0028] Due to the fact that it is difficult to produce cylinderinjection systems having identical operating characteristics, andbecause the main and anchor shots 72 and 74 occur close together, it ispossible that the duration of the anchor delay current signal 76 will beinsufficient to produce a split between the main and anchor shots 72 and74, i.e., a significant reduction in the fuel flow rate is not realized.This occurrence is known as a boot condition and is illustrated by theboot profile segment 82 shown in FIG. 2.

[0029] Depending on variables such as ambient operating conditions,desired engine performance, minimized emissions and so forth, it may beadvantageous, in certain scenarios, for the injectors to function in asplit mode. In other situations, it may be advantageous for theinjectors to function in a boot condition. Whichever mode is preferred,preferably all of the injectors function in the desired mode. To achievethe desired mode, the split/boot operating condition of each injector isdetected. Thereupon, injectors found to be operating in the undesiredcondition are corrected to function in the desired mode.

[0030] In one embodiment, the operating mode of an injector can bedetermined by monitoring changes in the volume of fuel desired by thegovernor when the engine is in a steady state condition. FIG. 3illustrates the difference in the volume of fuel delivered during thesplit mode, as shown by the split mode segment 80′, as compared to theboot mode, as shown by the boot mode segment 82′, for a given railpressure and main pulse signal 64 duration. The curve profile shown inFIG. 3 is representative of accumulated statistical data acquired fromthe performance test history of similar injector types, with ΔY being apredetermined value derived from the cumulative statistical averagedifference in fuel volume delivered between boot and split modes.

[0031] The operating mode of an injector can be altered by adjusting theduration of the anchor delay current signal. This is known as trimmingthe engine. A desirable magnitude of adjustment duration, known as theanchor delay current signal offset, is a predetermined value derivedfrom the statistical maximum duration of the boot condition, asrepresented by ΔX in FIG. 3.

[0032] A flow chart 84, having a first segment 86 illustrated in FIG.4a, shows the sequential process of the present invention for trimmingan engine, i.e., for detecting the operating mode of a given injectorand adjusting the mode as needed. As shown in box 88, the predeterminedΔX and ΔY values are recorded into the memory of the ECM 56.

[0033] In the preferred embodiment, the engine is operating at a steadystate speed. In addition the engine is also desirably operating at asteady state load. The ECM 56 then determines whether the engine speedand load are operating in a steady state, as indicated by decision box90. The values of the various engine trim lookup maps relied upon by theECM 56 include a corresponding fixed rail pressure and main shotduration. If the engine speed and load are not operating in a steadystate, the rail pressure and main shot duration will fluctuate, makingthe data in the lookup maps inaccurate. Therefore, if a steady state isnot detected, the engine trim test is abandoned, as indicated by box 92.

[0034] When the engine speed and load are determined to be in the steadystate, the average fuel volume requested by the governor (not shown) foran injection event is established, as shown in box 94. It should benoted that this is the volume of fuel desired to be delivered equally toall cylinders undergoing an injection event, as opposed to the volumedelivered to an individual cylinder.

[0035] The ECM 56 then selects a first cylinder for testing, asindicated in box 96. As shown in box 98, the anchor delay current signalduration is then increased by the anchor delay current signal offsetduration ΔX. Referring back to FIG. 3, it is clear that if the testedinjector was operating anywhere in a boot mode, i.e., anywhere along theboot mode segment 82′, under steady state conditions, an increase in theanchor delay current signal duration of ΔX will cause the injector toswitch to operating in a split mode, i.e., somewhere along the splitmode segment 80′. Accordingly, a notable reduction in fuel consumptionwill be realized. Conversely, if the tested injector was operating in asplit mode in the steady state, it will continue to operate in a splitmode when the anchor delay current signal duration is increased by ΔX.Accordingly, any change in fuel consumption will be negligible.

[0036] As seen in box 100, the new volume of fuel requested by thegovernor over several complete injection events is established andaveraged. The difference between the steady state volume of fuel and thenew volume of fuel for one injection event is then computed, as shown inbox 102. The difference may be between the steady state volume of fueland a specific volume of fuel for a specific injection event, or thevolume of fuel for the averaged fuel injection.

[0037] In decision box 104, the difference computed in box 102 iscompared to the predetermined ΔY volume. If the computed volume isgreater than the ΔY volume, the ECM 56 establishes that the injectorbeing tested was operating in a boot mode under steady state conditions,as indicated in box 106. Conversely, if the computed volume is less thanthe ΔY volume, the ECM 56 records that the injector was operating in asplit mode under steady state conditions, as shown in box 108.

[0038] In the preferred embodiment, the ECM 56 determines whether allcylinders have been tested, as illustrated by decision box 112 of asecond segment 110 of the flow chart 84 shown in FIG. 4b. If untestedcylinders remain, the ECM 56 selects the next cylinder for testing asindicated by box 114, and returns to box 98 of FIG. 4a to begin testingthe selected cylinder as previously explained.

[0039] In the preferred embodiment, upon testing all cylinders, the ECM56 determines whether it is desirable for all of the injectors tooperate in a desired, or pre-selected operating mode, such as a bootmode or a split mode, as shown by decision box 116. If it is desirableto have all injectors operate in a boot mode, the ECM 56 decreases theanchor current signal duration for each injector associated with acylinder found to be operating in a split condition by a duration of ΔX,as indicated in box 118. Conversely, if it is preferable for theinjectors to operate in a split mode, the ECM 56 increases the anchorcurrent signal duration for each injector associated with a cylinderfound to be operating in a boot condition by a duration of ΔX, asindicated in box 120.

[0040] In an alternative embodiment, the anchor delay current signal 76may be incrementally altered by a time value smaller than ΔX until amore precise value is determined for the anchor delay current signalduration that will yield a change in the injector operating mode.

[0041] In a further alternative embodiment, the ECM 56 is designed todetect the operating mode of an injector 14, and regulate it as desired,by monitoring the actual engine speed instead of, or in conjunction withthe fuel requested by the governor. A change in the fuel quantityinjected by an injector 14 due to switching from a boot mode to a splitmode will cause a corresponding change in engine speed, which will bedetected by the ECM 56 of this embodiment. In one embodiment, the changein speed may be determined by sensing the instantaneous firing speed ofa cylinder. The ECM 56 will adjust the anchor delay current signal 76 asneeded to cause the injector 14 to operate in the desired mode.

[0042] In one embodiment, the trimming technique disclosed may beapplied to any injection signal having two injection shots. For example,an injection signal including a pilot and main injection, or a pilot andanchor injection, or a main and anchor injection.

Industrial Applicability

[0043] Utilization of an injection method and system in accordance withthe present invention provides for better emission control duringcertain engine operating conditions as explained above. Although aparticular injection waveform for delivering multiple fuel injectionsmay vary depending upon the particular engine operating conditions, thepresent system is capable of determining the timing associated with theanchor delay current signal regardless of the type of electronicallycontrolled fuel injectors being utilized, and regardless of the type offuel being utilized. In this regard, the appropriate fuel maps can bestored or otherwise programmed into the ECM 56 for use during any steadystate condition of the engine. These operational maps, tables and/ormathematical equations stored in the programmable memory of the ECM 56determine and control the various parameters associated with theappropriate multiple injection events to achieve desired emissionscontrol.

[0044] It is recognized that variations to the steps depicted inflowchart 84 (FIGS. 4a and 4 b) could be made without departing from thespirit and scope of the present invention. In particular, steps could beadded or some steps could be eliminated. All such variations areintended to be covered by the present invention.

[0045] As is evident from the foregoing description, certain aspects ofthe present invention are not limited by the particular details of theexamples illustrated herein and it is therefore contemplated that othermodifications and applications, or equivalencies thereof, will occur tothose skilled in the art. It is accordingly intended that the claimsshall cover all such modifications and applications that do not departfrom the spirit and scope of the present inventions.

[0046] Other aspects, objects and advantages of the present inventioncan be obtained from a study of the drawings, the disclosure and theappended claims.

1. A method for trimming an engine operating in a steady state so that aplurality of injectors contained therein operate in a pre-selected mode,the method comprising: determining that a speed and a load of the engineare operating in a steady state; selecting one of the plurality ofinjectors; detecting an operating mode of the selected injector;recording the operating mode of the selected injector; sequentiallyrepeating the above processes for each remaining unselected injector;comparing the recorded operating mode of the selected injector to thepre-selected operating mode to determine which of the selected injectorsis not operating in the pre-selected operating mode; and changing thedetected operating mode to the pre-selected mode for each of theselected injectors detected to be operating in other than thepre-selected operating mode.
 2. A method for trimming an engine in asteady state so that a plurality of injectors contained therein operatein a desired operating mode, the method comprising: determining that aspeed of the engine is operating in a steady state; detecting anoperating mode of one of the plurality of injectors; comparing thedetected operating mode of the one of the plurality of injectors to thedesired operating mode to determine if the injector is operating in thedesired operating mode; and changing the detected operating mode to thedesired operating mode for the one of the plurality of injectors.
 3. Themethod, as set forth in claim 2, further comprising the step ofdetermining the engine is operating in a steady state load.
 4. Themethod, as set forth in claim 2, further comprising the steps of:detecting an operating mode of each of the plurality of injectors;comparing the detected operating mode of each of the plurality ofinjectors to the desired operating mode to determine which of theinjectors is not operating in the pre-selected operating mode; andchanging the detected operated mode to the desired operating mode foreach of the plurality of injectors detected to be operating in otherthan the desired operating mode.
 5. The method, as set forth in claim 3,wherein the injector modes of operation include a split mode and a bootmode.
 6. The method, as set forth in claim 5, wherein an electroniccontrol module in electrical communication with the engine determinesthe pre-selected mode by referring to lookup maps.
 7. The method, as setforth in claim 6, wherein each injector delivers fuel to a respectivecylinder during repeated injection events.
 8. The method, as set forthin claim 5, wherein an anchor delay current signal occurs for a portionof each injection event.
 9. The method, as set forth in claim 8, whereinthe step of determining the operating mode of the selected injectorincludes the steps of: establishing a statistical average difference inthe volume of fuel delivered between a boot mode and a split mode;establishing a anchor delay current signal offset; establishing a steadystate volume of fuel delivered by all of the injectors for an injectionevent; increasing the anchor delay current signal duration by thepredetermined anchor delay current signal offset to cause a new volumeof fuel to be delivered by the injectors; recording the new volume offuel delivered by the injectors; computing a difference between thesteady state fuel volume and the new fuel volume; and determiningwhether the difference between the steady state fuel volume and the newfuel volume is greater than the predetermined statistical averagedifference in the volume of fuel delivered between a boot mode and asplit mode.
 10. The method, as set forth in claim 9, wherein the step ofrecording the operating mode of the selected injector includes the stepof recording that the selected injector was operating in the boot modebefore increasing the duration of the anchor delay current signalduration if the difference between the steady state fuel volume and thenew fuel volume is greater than the predetermined statistical averagedifference in the volume of fuel delivered between a boot mode and asplit mode, and includes the step of recording that the selectedinjector was operating in the split mode before increasing the durationof the anchor delay current signal duration if the difference betweenthe steady state fuel volume and the new fuel volume is less than thepredetermined statistical average difference in the volume of fueldelivered between a boot mode and a split mode.
 11. The method, as setforth in claim 10, wherein the step for altering the operating mode of aselected injector includes the step of altering the duration of theanchor delay current signal by the predetermined anchor delay currentsignal offset.
 12. A fuel injection control system for trimming anengine in a steady state so that a plurality of injectors containedtherein operate in a pre-selected mode, the apparatus comprising: anengine speed sensor; an engine load sensor; an electronic control modulein electrical communication with the engine speed sensor and the engineload sensor; wherein the electronic control module is operable, upondetermining that the engine speed and load are in a steady state, toselect a previously unselected injector; to determine the operating modeof the selected injector; to record the operating mode of the selectedinjector; to sequentially repeat the operations of selecting apreviously unselected injector; to determine the operating mode of theselected injector and record the operating mode of the selected injectorfor each of the plurality of injectors; to compare the recordedoperating mode of each injector to the pre-selected operating mode todetermine which of the selected injectors is not operating in thepre-selected operating mode; and to change the detected operating modeto the pre-selected mode for each of the injectors determined to beoperating in other than the pre-selected operating mode.
 13. The fuelinjection control system, as set forth in claim 12, wherein the injectormodes of operation include a split mode and boot mode.
 14. The fuelinjection control system, as set forth in claim 13, wherein theelectronic control module determines the pre-selected mode by referringto lookup maps.
 15. The fuel injection control system, set forth inclaim 14, wherein each injector delivers fuel to a respective cylinderduring repeated injection cycles.
 16. The fuel injection control system,as set forth in claim 15, wherein an anchor delay current signal occursfor a portion of each injection event.
 17. The fuel injection controlsystem, as set forth in claim 16, wherein the electronic control moduledetermines the operating mode of the selected injector by recording apredetermined statistical average difference in the volume of fueldelivered between a boot mode and a split mode; recording apredetermined anchor delay current signal offset; recording a steadystate volume of fuel delivered by all of the injectors for an injectionevent; increasing the anchor delay current signal duration by thepredetermined anchor delay current signal offset to cause a new volumeof fuel to be delivered by the injectors; recording the new volume offuel delivered by the injectors; computing a difference between thesteady state fuel volume and the new fuel volume; and determiningwhether the difference between the steady state fuel volume and the newfuel is greater than the predetermined statistical average difference inthe volume of fuel delivered between a boot mode and a split mode. 18.The fuel injection control system, as set forth in claim 17, wherein theelectronic control module records the operating mode of the selectedinjector by recording that the selected injector was operating in theboot mode before increasing the duration of the anchor delay currentsignal duration if the difference between the steady state fuel volumeand the new fuel volume is greater than the predetermined statisticalaverage difference in the volume of fuel delivered between a boot modeand a split mode, and by recording that the selected injector wasoperating in the split mode before increasing the duration of the anchordelay current signal duration if the difference between the steady statefuel volume and the new fuel volume is less than the predeterminedstatistical average difference in the volume of fuel delivered between aboot mode and a split mode.
 19. The fuel injection control system, asset forth in claim 18, wherein the electronic control module changes thedetected operating mode of a selected injector to the pre-selected modeby altering the duration of the anchor delay current signal by thepredetermined anchor delay current signal offset.
 20. A method fortrimming an engine having at least one injector controllable by anelectronic control signal, the engine having an engine speed and load,the method comprising: detecting an operating mode of each injector. 21.The method, as set forth in claim 20, including the step of modifyingthe electronic control signal to each injector.
 22. The method, as setforth in claim 21, including the step of detecting an operating mode ofeach injector generated by the modified electronic control signal. 23.The method, as set forth in claim 22, wherein the injector modes ofoperation include a split mode and a boot mode.
 24. The method, as setforth in claim 23, wherein the characteristics of the electronic controlsignal are determined in accordance with lookup maps associated with theengine.
 25. The method, as set forth in claim 24, wherein each injectordelivers fuel to a respective cylinder during repeated injection events.26. The method, as set forth in claim 25, wherein the electronic controlsignal includes an anchor delay current signal for a portion of eachinjection event.
 27. A method for trimming at least one fuel injectiondevice associated with an engine, the injection device injectingmultiple fuel shots in accordance with an electronic control signalgenerated by the engine during a fuel injection event, the methodcomprising the steps of: sensing a first engine speed; modifying theelectronic control signal; sensing a second engine speed; anddetermining an operating mode of the at least one fuel injection devicein response to said first and second engine speeds.
 28. A method, as setforth in claim 27, wherein the operating modes include a split mode anda boot mode.
 29. The method, as set forth in claim 28, wherein eachinjection device delivers fuel to a respective cylinder during repeatedinjection events, the injection event including a first injection and asecond injection and an injection delay between the first and secondinjections.
 30. The method, as set forth in claim 29 wherein the step ofmodifying the electronic control signal further comprises the step ofmodifying the injection delay.
 31. The method, as set forth in claim 29,wherein the step of modifying the electronic control signal furthercomprises the step of increasing the injection delay by a predeterminedamount.
 32. The method, as set forth in claim 29, wherein the step ofdetermining the operating mode of said first and second engine speedsfurther comprises the steps of determining a difference between saidfirst and second engine speeds; and determining the operating mode is asplit injection mode when said difference is less than a predeterminedthreshold.
 33. The method, as set forth in claim 29, wherein the step ofdetermining the operating mode of said first and second engine speedsfurther comprises the steps of determining a difference between saidfirst and second engine speeds; and determining the operating mode is aboot injection mode when said difference is greater than a predeterminedthreshold.